[The protein antigens of Streptococcus pneumoniae]

Protein preparations of three S. pneumoniae strains belonging to different serological types according to the structure of their capsular polysaccharides have been analyzed. Immunoblotting with antiserum to a protein preparation isolated from one strain, pooled serum of patients with pneumococcal infection and individual sera of such patients have revealed that different S. pneumoniae strains have serologically active proteins with similar molecular weights. Analysis made with the use of rabbit antiserum to a protein preparation has demonstrated that most of such preparations (mol. wt. of 44, 49, 50 kD, etc.) belong to the group of proteins Pnp II, average in their molecular weight among the preparations under study (23-53 kD). At the same time serological response in pneumococcal infection is linked with common S. pneumoniae proteins with mol. wt. of 50, 87 and 97 kD, but not always with pneumolysin.